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[SAFE|safe:Home] version 12 allows importing of [spectrum load cases|kb:Response-spectrum analysis] from [ETABS|etabs:Home]. The export response spectrum cases option in ETABS will only be available after you run the analysis.
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h1. Load patterns
The [load patterns|kb:Load pattern] relevant to response spectrum imported into SAFE will be:
* *SPECXECC* - These are static loads resulting from spectrum eccentricity only. One for each spectrum case will be imported. Even if no eccentricity has been specified in ETABS, this load pattern will still be imported; however, in this case values will be zero.
* *MODAL 1, 2, ..., i, ... n* - These are the load vectors for every mode and n is the number of modes in ETABS model.
h1. Load cases
The [load cases|kb:Load case] relevant to Response spectrum imported into SAFE will be:
* *SPECXECC* - Linear static case result of spectrum eccentricity, one for each spectrum case.
* *MODAL* - Load type case Modal, this is a load vector of modal loads.
* *SPECX* - Response spectrum case, one for each spectrum case imported.
h1. Other comments
Please notice that when using default [load combinations|kb:Load combination], spectrum cases will be combined assuming "QUAKE" type load, also when observing forces on elements, combinations involving spectrum cases will be defined as envelope type resulting in maximum and minimum values. Static load cases from spectrum eccentricity will be imported and flagged as "OTHER" load type, and need to be added manually to other load combinations as required.
For uplift foundation analysis, it is not possible to convert combinations involving spectrum cases to nonlinear uplift cases, due to the fact that response spectrum analysis only applies to linear analysis. You could use Response Spectrum story forces to apply as user defined lateral load case in your ETABS model and export the lateral loads results to SAFE for foundation design. Please notice this is not required for | Info |
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NOTE: The option to export response-spectrum load cases from ETABS into SAFE becomes available once analysis is run in ETABS. Cases may then be imported into SAFE. |
Load pattern
The response-spectrum load patterns imported into SAFE include:
- SPECXECC represents linear-static loads which result only from spectrum eccentricity. One will be imported per spectrum case, regardless of whether or not eccentricity is specified. If no eccentricity is specified, values will be zero.
- MODAL 1, 2, ... n represents the load vectors associated with each of the n modes.
Load case
The response-spectrum load cases imported into SAFE include:
- SPECXECC represents linear-static loads which result only from spectrum eccentricity. One will be imported per spectrum case, regardless of whether or not eccentricity is specified. If no eccentricity is specified, values will be zero.
- MODAL represents the load vectors associated with each of the n modes.
- SPECX represents the response-spectrum case. One will be imported per spectrum case.
- When using default load combinations, spectrum cases will be combined by assuming a QUAKE load type.
- Load combinations which include response-spectrum load cases will be defined with an ENVELOPE load type. Maximum and minimum values will be associated element-force results.
- Static load cases from spectrum eccentricity will be imported and flagged as OTHER load type. These cases may be manually added to load combinations as necessary.
- For foundation analysis and design, nonlinear uplift cases may not be converted from spectrum combinations because response-spectrum analysis is a linear formulation. As an alternative, spectrum story forces may be applied within ETABS manually as a lateral load case, then response may be exported to SAFE for foundation design.